Conventional thin film magnetic recording disks typically comprise a substrate, such as an aluminum alloy disk with a nickel-phosphorus (NiP) surface film, a film of magnetic metal alloy or metal oxide formed on the substrate, and a protective overcoat formed over the magnetic film. Such disks may be fabricated by evaporating or plating the magnetic film on the substrate, or in the more conventional approach by sputter depositing the magnetic film.
Regardless of the specific composition of the magnetic film or the method of fabrication of the disk, all such commercially available disks utilize a continuous film of the magnetic metal alloy or metal oxide. Thus, during operation of the disk file, data may be recorded at any radial position of the disk where the continuous magnetic film is deposited. Because the read/write head cannot always be precisely aligned over any predetermined radial position on the disk, new data recorded over a previously recorded track may be recorded on the disk in a radial position slightly offset from the track where the previous data was recorded. This may occur even though the previous data and the new data are identified as having been recorded on the same data track. When the read/write head reads the signal from this track it will also pick up previously recorded signals on the disk at the edges of the track. An additional problem with the use of continuous magnetic film in thin film disks is that because magnetic media extends radially on the disk on both sides of the read/write head, fringe magnetic fields from the read/write head during recording will generate magnetic patterns at the edges of the track. This creates disorientation of the magnetic domains in the film at the track edges which results in noise when the recorded signal is read back. Conventional thin film disks which have a continuous magnetic film also require a nonmagnetic overcoat of sufficient thickness to not only passivate the magnetic film from the atmosphere but also to provide a durable protective barrier when the disk surface is contacted by the air bearing slider which supports the read/write head.
In order to overcome the above shortcomings, thin film disks with discrete magnetic tracks separated by discrete nonmagnetic guard bands or separator tracks have been proposed. A variation of such a discrete track disk is described in Great Britain Patent specification 1,443,248. In the '248 patent, discrete tracks of low coercivity magnetic oxide are formed from a continuous film of magnetic oxide by ion implanting cobalt ions through a mask to generate concentric spaced-apart high coercivity separator tracks. The cobalt-doped high coercivity separator tracks may also serve to record head positioning servo information. The IBM Technical Disclosure Bulletin (TDB), October 1975, at page 1641, describes a discrete track thin film disk formed by depositing a film of iron or cobalt over a resist pattern previously formed on a thin film of alpha iron oxide. The disk structure is then annealed to diffuse the iron or cobalt into the alpha iron oxide to transform it into ferromagnetic material. When the resist is removed, the result is a disk with discrete magnetic tracks separated by discrete tracks of nonmagnetic alpha iron oxide. The IBM TDB, January 1980, at page 3268, describes a discrete track disk in which the discrete magnetic tracks are formed by depositing a magnetic film (or magnetic particles) into concentric grooves which have been preformed on a substrate. Japanese Kokai 58-212624 describes a discrete track thin film disk in which concentric separator tracks are formed on a continuous magnetic iron oxide film by laser radiating the disk in a concentric track pattern so as to render the concentric tracks of the iron oxide film non magnetic. Japanese Kokai 59-112434 describes a particulate disk (i.e. a disk with a conventional magnetic coating of iron oxide particles dispersed in an organic binder) in which gaps are generated in the organic coating by forming a patterned photoresist film over the organic coating and then acid etching the organic coating.